Farsightedness decreased in lasik patients
Most patients who undergo
refractive surgery to correct imperfections in their vision come out of the procedure
with eyesight that is 20/20 or better. However, researchers have come to realize
that fixing imperfections can affect vision in unexpected ways — some patients
exit the surgery slightly farsighted or nearsighted.
A study conducted five years ago on 340 eyes showed
that 74 of the eyes treated, or 21.8 percent, were slightly farsighted. At the European
Society of Cataract and Refractive Surgery meeting in London in September, Dr.
Scott MacRae of the University of Rochester Eye Institute presented the results
of a new study that shows a significant drop in farsightedness among patients who
underwent lasik surgery.
MacRae and his colleague Manoj Venkiteshwar
developed a formula called the University of Rochester Nomogram that predicts which
patients are more likely to be farsighted after the lasik procedure and that adjusts
the laser accordingly. The complex computer formula controls how the laser beam,
which hits the cornea at about 50 times per second with 750 to 3000 pulses, moves
around on the surface of the cornea. The surgeon can then sculpt the cornea into
the right shape so that it produces as flawless an image as possible.
MacRae and his colleagues at the university
tested 445 eyes using the formula and found that only six eyes, or 1.3 percent,
were slightly farsighted after lasik — a dramatic decrease from the results
of five years ago.
The researchers plan to continue working
to improve patients’ vision, building on the work of David Williams, also
at the University of Rochester. Williams first developed the system that enables
doctors to see subtle imperfections in the eye.
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